The present invention relates to improved oxygen-absorbing compositions and to a method for absorbing oxygen rapidly from a closed container without generating hydrogen.
In certain applications where oxygen has to be absorbed rapidly from a closed container, the oxygen-absorbing composition is provided with an acidic environment, either by injecting an acid or injecting water to activate a dry acid in the composition.
One example of the foregoing is described in U.S. Pat. No. 5,928,560 which discloses a packet of an oxygen-absorbing composition which is rapidly activated by the injection of an acid, such as acetic acid, or the injection of water where a dry acid is present. The prior art composition which is injected with an acid includes iron, an electrolyte salt, such as sodium chloride, and a carbonate which releases carbon dioxide. The prior art composition which contains the foregoing components and an acid salt is injected with water. The injected packet is inserted into a flexible package containing an oxygen-sensitive product. However, the foregoing oxygen-absorbing compositions had a serious drawback because incidental to the oxygen-absorption, hydrogen gas was generated which could bloat the flexible package containing the oxygen-sensitive product.
Another example of a prior oxygen-absorbing composition is disclosed in U.S. Pat. No. 6,538,571 wherein the foregoing problem of hydrogen gas generation was overcome by including an inhibited carbon dioxide generating compound so that it created a less acidic environment after rapid oxygen absorption, and this less acidic environment reduced the concentration of hydronium ions in solution to thereby inhibit the generation of hydrogen gas to insignificant levels.